Common types of inkjet printers include single-pass systems and shuttle based systems (i.e., multi-pass systems). FIG. 1A illustrates an example of printing using a single-pass system. The printer includes one or more printheads that span the width of the printer, which is perpendicular to the direction of the paper transport. The printheads can access reservoirs of ink to print an image on media that advances under the printheads in a downstream direction. An image is a perceptible representation (e.g., a document, a banner, or a graphic) that can be recorded (e.g., printed) on media (e.g., physical substrates such as paper or tile). The printheads can dispense different inks to print a colored image on the media.
FIG. 1B illustrates an example of printing using a shuttle based system. As shown, printing involves multiple “passes” of a carriage (not shown) including a printhead that moves perpendicular to the direction that the media advances over a printing area. With each pass, ink can be dispensed onto a medium to print an image. Hence, the carriage can pass the printheads over media multiple times to produce full-color results.
The printheads of inkjet printers eject drops of ink through small openings onto media. These small openings are commonly referred to as ejection nozzles. Each drop of ink forms a printed dot on media. A printed image is formed from numerous pixels that can include printed dots. The nozzles can fail to operate properly when, for example, they become clogged with debris. When this occurs, printing is stopped to clean or replace the defective printer nozzles. Accordingly, existing techniques for correcting for defective printer nozzles are counterproductive and unfit for modern high speed printers.